Long Term Evolution (LTE) release 12 is intensively in research to enhance performance in light of capacity, transmission coverage, inter-cell coordination and costs. For such performance enhancement, an introduction of various technologies is being discussed such as small cell enhancement, macro cell enhancement, new carrier-type and machine-type communications, in the LTE release 12 technology.
Enhanced capacity and transmission coverage, which are aimed by the LTE release 12, may be achieved by small cell enhancement based on inter-site carrier aggregation, LTE-Wireless Local Area Network (WLAN) incorporation, and macro cell enhancement. As the size of a cell decreases, user equipment's cell-to-cell move frequently happens, and upon user equipment's move, the amount of traffic signaled may increase. To address such problem, the small cell may be optimized by reducing signaling from an Radio Access Network (RAN) to a core network using small cell enhancement.
The New Carrier Type (NCT) is a frame type newly defined differently from the legacy frame configuration. The NCT may be a carrier type optimized for small cells, but may apply to macro cells as well. The NCT reduces overhead that is generated due to transmission of Cell-specific Reference Signal (CRS) and may demodulate a downlink control channel based on the Demodulation Reference Signal (DM-RS). By newly defining NCT, the energy of the base station may be saved or interference that occurs in a Heterogeneous Network (HetNet) may be reduced. Further, by using NCT, reference signal overhead, which is caused when a plurality of downlink link antennas is used to transmit data, may be decreased. More specifically, although the NCT maintains the existing frame structure (e.g., CP length, subframe structure, duplex mode), it may be defined as a carrier having a different structure of a reference signal that is subject to actual transmission, which is not backward compatible (to rel-11 and below UEs).